Electrode for use in an electrochemical treatment process

ABSTRACT

An electrode comprises an outer tube containing a spiral inner electrode which surrounds a rod held at its ends by fittings in the ends of the tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK

Not Applicable

BACKGROUND OF THE INVENTION

The invention relates to an electrode.

In our EP-0883700B we have described and claimed an electrode for use inelectrochemical treatment of metal reinforced concrete, the electrodecomprising a generally cylindrical body formed of porous material, thebody having an external surface and an internal surface, a power supplyconductor in use, being in electrical contact with the internal surfaceand with a supply of electrical current. The body wall is porous toallow ingress of gas and is preferably formed of a titanium suboxide ofthe formula TiO_(x) where is 1.55 to 1.95.

When electrode bodies are required to be supported at their extremeends, in electrochemical cells, rather than being encased in concrete,it is often necessary to provide specially shaped end caps. If these aresimply attached with adhesives, the adhesives often fail in theextremely aggressive electrochemical environment. If mechanical means ofattachment is used, then the electrode material itself is subject tomechanical forces, which may damage the body if the material is brittle,since the wall of the body will not withstand high compressive andtorsional forces when end caps are inserted. Such strains arise forexample when too much force is used to tighten up nuts and can cause thebody to fracture.

It is one object of the invention to provide an electrode having agenerally tubular body and end fittings which are easy to assemble andfix in place without any major mechanical stresses being applied to thebody. It is another object of the invention to provide such an electrodein which the end fittings tend to align an elongate support for theinternal electrode.

BRIEF SUMMARY OF THE INVENTION

According to the invention in one aspect there is provided an electrodecomprising a generally tubular body having an external surface and aninternal surface, an elongate rod extending between the ends of the bodyand having at least one end fitting at an end of the body, a powersupply conductor being present in the annulus between the rod and theinner surface and in contact with that inner surface, and in use, inconnection with a power supply.

Preferably an end fitting in the form of a cap is present at one or bothends of the tubular body to close one or both ends, the or each caphaving an inner end portion shaped to hold and contribute to thecentralisation of the cap and engage the inner surface of the endportion of the body without stressing the body. Most preferably theengaging means of the inner portions comprises radially spaced apartflexible flutes or vanes. Most preferably the flutes or vanes are at anangle to the true radial direction such that once compressed the flutesor vanes will be bent in the same radial direction to farther assist thecentralisation. Most preferably the flutes or vanes are sufficientlytough and flexible to provide an element of flexibility in the axis ofthe end cap with respect to the axis of the tubular body, thus reducingbending stresses on the body, and also allowing the use of bodies withslightly variable internal diametric tolerances.

It is also preferred that the inner end portions of the caps each definea socket to receive an end portion of the rod to space the two end capsat an appropriate distance to ensure that axial compressive forces aretransmitted along the rod rather than along the body. Preferably, theends of the rods are provided with a clip system in each socket so thatonce engaged the rod cannot be withdrawn. In this way any axialextensional forces will tend to be are borne by the rod instead of thecylindrical body.

Preferably, all the components of the fittings can be manufactured byinjection moulding of thermoplastic polymers which is a cheap highvolume method, and thus results in cost effective electrodes.

The body may be formed of an electrically conductive ceramic materialwhich will tend to be brittle. The body may be inherently electricallyconductive or it may be covered with a coating of such a material.

The tubular body may be of a suitable shape, e.g. generally cylindricalor prismatic.

An electrode of the invention is very versatile and may be used as ananode or a cathode in many electrochemical reactions such as:

-   -   electrochemical water sterilisation;    -   electrochemical destruction of organics compounds such as        pesticides and or pseudo-oestrogenic compounds in water;    -   electrochemical treatment of sewage;    -   electrochemical synthesis of fine chemicals; and    -   electrochlorination of water for, for instance, swimming pools.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order that the invention may be well understood it will now bedescribed by way of example only with reference to the accompanyingdiagrammatic drawings, in which:

FIG. 1 is an exploded perspective view of one anode assembly of theinvention;

FIG. 2 is a longitudinal sectional view of the anode of FIG. 1;

FIG. 3A is a perspective view of one end cap and FIG. 3B is an end viewthereof;

FIG. 4 is a perspective view of an extension cap, and

FIG. 5 is an enlarged view of the area on FIG. 2 marked ‘V’ and showingthe end of the anode from which a wire emerges.

DETAILED DESCRIPTION OF THE INVENTION

The anode assembly includes two elongate tubes 1, 1A arranged end toend. The tube 1 is made of titanium suboxide available under theregistered trade mark EBONEX. The tube 1A is moulded of a plastics. Thewall of the tube 1 is solid along its length, whereas the tube 1A issolid save for a slot 2 at one end 3. The tube 1 contains an elongatesupport rod 4 which holds two caps E1, E2 in place, as will be explainedbelow. A conductor wire 5 formed of titanium spring metal is present asa spiral about the rod 4 and has a straight tail 6 which emerges fromthe tube 1A at the end 3. This will be explained in better detail below.

As shown in FIGS. 3A and 3B, the cap E1 consists of a cylinder havingtwo longitudinal end portions 10, 11, separated by a shoulder 12. Endportion 10 is shorter than the end portion 11. Six vanes are shown, butthe number is not critical. The vanes are arranged so that they willflex in the same direction. The end portion 11 has inwardly turnedreverse facing longitudinal spring tongues 15 located to be snap-engagedin slots 16 near the ends of the rod 4. An inner partition 17 is presentto separate the two end portions and an inner shoulder 18 is present inthe end portion 11, to act as an abutment for the end of the rod 4 sothat the tongues 15 will align with the slots 16. The cap E1 is receivedin and engages in one end of the tube 1.

The second end cap E2, has the same vane or fluting as E1, but differsin the presence of hole 19, whereby the electrical connection wirepasses through E2. The end portion 10 of E2 is illustrated to be asinterference fit with tube 1A. (This joint however could be made with anadhesive or with a friction or other welding technique). Tube 1A ispresent in this illustration to provide a smooth seal surface to allowthe electrode to pass through the wall of the electrochemical cell, andso that the electrical connection from the power supply is outside thecell and easy to access.

The wire 6 passes through the end of tube 1A through a hole, which isprovided with a sealing system, such as is illustrated. Sealant can beinjected into hole 2 and fill the annulus around the wire preventing anyleakage of electrolyte through the end of tube 1A.

The electrical connection can be made directly to the exposed end ofwire 6, but in this example, the tube 1A is provided with a shortthreaded stud 25, around which can be bent the end of the wire 5,supported by washer 27, to present a neat terminal for the electricalconnection.

Typically the electrode is assembled by inserting the straight part 6 ofwire 5 through hole 19 in E2 and then pressing tube 1A into place on E2with wire 5 extending through the tube 1. Rod 4 is then placed into thesocket in E2 and engaged with the clip. An assembly tool, not shown, isthen used to “wind up” the spring part of wire 5, thus reducing itsdiameter such that the body 1 can be slid over it and onto the flutes ofE2 probably with a slight rotation. Because the vanes flex in the samedirection, they will tend to bend and reduce the overall diameter of thecap and act as a self-centring system. The spring is then released andallowed to engage on the internal surface of tube 1. E1 is then pressedinto place, also with a slight rotational movement until it is capturedby the clip engaging into rod 4, also with the flutes acting as aself-centring system similar to E2. Washer 26 is added and the wire bentaround stud 25. Finally sealant is injected into slot 2.

The flutes can also accommodate tubes of different diameters, as well assome flexibility to eliminate bending stresses.

The support rod is positively engaged at both ends, which capture therod and eliminates both compressive and extensive forces on the ceramictube.

Because all the parts lock together mechanically, there is no need foradhesives.

SEQUENCE LISTING

Not Applicable

1. An electrode for use in an electrochemical treatment process, theelectrode comprising: (i) an elongate generally tubular electrode bodymade of relatively brittle material, said body having an interior havingan inner surface and an axis extending through the interior of theelectrode body; (ii) an elongate support member parallel to said axiswithin said interior of the electrode body; (iii) spacer means coupledbetween the elongate support member and the electrode body for locatingradial and axial positions of the electrode body relative to theelongate support member, the spacer means comprising resilient portionsengaged with the electrode body for resiliently maintaining radialspacing between the electrode body and the elongate member; (iv)electrical conductor means in the interior of the electrode body formaking electrical contact with the inner surface of the electrode bodyat a plurality of positions spaced along said axis.
 2. An electrodeaccording to claim 1, wherein said spacer means comprises two spacermembers positioned at respective ends of the electrode body and eachspacer means comprising the resilient portions engaged with theelectrode body.
 3. An electrode according to claim 1, wherein saidresilient portions comprise a plurality of flutes extending radiallyoutwardly into engagement with the inner surface of the electrode body.4. An electrode according to claim 1, wherein said resilient portionscomprise a plurality of flexible vanes extending radially outwardly intoengagement with the inner surface of the electrode body.
 5. An electrodeaccording to claim 1, wherein said spacer means is connected to theelongate support member by a spring tongue means fixed to the spacermeans and operable to snap engage apertures formed in the elongatesupport member.
 6. An electrode according to claim 1, wherein saidspacer means comprises two caps at respective ends of the electrode bodyand operable to close the electrode body at said ends.
 7. An electrodeaccording to claim 1, wherein said spacer means includes an end fittingcomprising a tubular portion having a plurality of radially outwardlyextending flexible vanes and a shoulder portion adjacent the tubularportion for engaging the inner surface and an end of the electrode body,said end fitting comprising electrode mounting means in the form ofanother tubular portion extending axially from the shoulder away fromthe first-mentioned tubular portion and having a plurality of radiallyoutwardly extending flexible vanes.
 8. An electrode according to claim1, wherein the electrical conductor means is a coiled spring for beingwound up to enable it to be entered into said electrode body and thenreleased so that its coils unwind and expand into electrical contactwith the inner surface of the electrode body.
 9. An electrode accordingto claim 1, wherein said electrode body is made of electricallyconductive ceramic material.
 10. An electrode according to claim 1,wherein said electrode body is made of ceramic material having a coatingof electrically conductive material thereon.
 11. An electrode accordingto claim 1, wherein said electrode body is made of titanium suboxide.12. An electrode for use in an electrochemical treatment process, theelectrode comprising: (i) an elongate generally tubular electrode bodyhaving a longitudinal axis and an inner surface and made of relativelybrittle electrically conductive ceramic material; (ii) two end fittingsmade of plastics material and having respective plug portions extendinginto respective ends of the tubular electrode body arid havingrespective shoulder portions in axial engagement with the ends of theelectrode body; (iii) an elongate support rod extending through theelectrode body and coupled to said two end fittings; (iv) locating meansat respective ends of the elongate support rod and operable to fix axialpositions of the end fittings relative to the elongate support rod andavoid stress applied axially to the electrode body; (v) resilientsupport means connected between said plug portions and the inner surfaceof the tubular electrode body for supporting the electrode body radiallyand maintaining radial spacing between the end fittings and theelectrode body while avoiding radial stress on the electrode body; (vi)an elongate electrically conductive member coiled around the elongatesupport rod between the elongate support rod and the electrode body andin electrical contact with the inner surface of the electrode body at aplurality of positions along said axis.
 13. An electrode according toclaim 12, wherein the end fittings comprise respective mounting portionsextending from the shoulder portions in respective directions away fromthe electrode body, each mounting portion having radially outwardlyextending vanes.
 14. An electrode according to claim 13, including atubular extrusion portion engaged over the vanes of the mounting portionat one end, said electrically conductive member being connected to anelectrical supply tail that leads from inside the electrode body to theoutside of the electrode through the end fitting at said one end of theelectrode and through said tubular extension portion.